emacs: implements toggling of error display (#148).
emacs: implements toggling of error display (#148).

dra27/merlin,chambart/merlin,neojski/merlin,fxfactorial/merlin,ocaml/merlin,rgrinberg/merlin,chambart/merlin,ocaml/merlin,the-lambda-church/merlin,the-lambda-church/merlin,rgrinberg/merlin,the-lambda-church/merlin,neojski/merlin,fxfactorial/merlin,fxfactorial/merlin,chambart/merlin,rgrinberg/merlin,dra27/merlin,haselwarter/merlin,fxfactorial/merlin,haselwarter/merlin,chriskonstad/merlin,haselwarter/merlin,ocaml/merlin,haselwarter/merlin,dra27/merlin,rgrinberg/merlin,neojski/merlin,dra27/merlin,chambart/merlin,neojski/merlin,chriskonstad/merlin,ocaml/merlin